A new laboratory analysis of eight prescription drugs that expired between 28 and 40 years ago has found that most have remained just as potent as they were on the day they were made. Overall, the eight drugs included 14 different active ingredients, including aspirin, codeine and hydrocodone. In 86% of cases, the study found, the amount of active ingredient present in the drugs was at least 90% of the amount indicated on the label. That falls within the range deemed acceptable by the Food and Drug Administration. It's impossible to say from the study results alone whether the eight drugs would be effective if used today, but there's no reason to think that they're not," says Lee Cantrell, the lead author of the study and a professor of clinical pharmacy at the University of California, San Francisco. Most drugs are dated to expire after one to five years, but as the results show, that time frame doesn't necessarily correlate to a drug's potency, Cantrell says. "All [the expiration date] means from the manufacturers' standpoint is that they're willing to guarantee the potency and efficacy for the drug for that long," he says. "It has nothing to do with the actual shelf life." "We're spending billions and billions on medications and medication turnover," Cantrell says. "If a drug has expired, you've got to throw it away, it goes into a landfill, and you have to get a new prescription. This could potentially have a significant impact on cost."